<?php
class A{
    public static function who()
    {
        echo "A的who方法";
    }
    public static function test()
    {
        //self::who(); 输出结果:"A的who方法",调用自身who()
        static::who(); //使用关键字static实现后期绑定,调用b类的who
    }
}
class B extends A{
    public static function who()
    {
        echo "B类的who方法";
    }
}
B::test();